1. Field of the Invention
The present invention relates to a printer, more specifically to a printer capable of a power saving control.
2. Description of the Related Art
In recent years, a demand for the power saving in the field of electronics such as printers has increasingly expanded. For example, to meet such a demand, the electronics field has provided a printer that realizes to save a power by shifting a data transfer mode into a sleep mode while the data is not transferred and releasing the sleep mode when the data transfer is detected.
For example, the Japanese Published Unexamined Patent Application No. Hei 8-324071 has disclosed a printer control unit in which, while the supply of power to the units of the printer main frame except the units having communication functions with the host processor is shifted into the sleep mode when information is received from the host processor, the control unit including a CPU, ROM, RAM, etc., analyzes the information received, judges whether to or not to receive information to start the supply of power, and controls whether to or not to resume the supply of power in accordance with the judgment result. According to this printer control unit, the printer control unit is not needed to resume the supply of power unnecessarily every time it receives data from the host processor, which effects to restrain the power consumption.
However, in the foregoing conventional technique, the printer control unit is always monitoring whether to or not to receive the information to start the supply of power, and accordingly, the supply of power to the CPU, ROM, RAM, etc., that constitute the control unit is always necessary, which accompanies power consumption even in the sleep mode. In recent years, however, the power consumption by the CPU concerned with the communication control and the memories such as ROM, RAM, etc., is no longer considered negligible. Accordingly, it is necessary to reduce the power consumption not only by the printer main frame but by the CPU concerned with the communication control and the ROM, RAM, etc.